A phage display system for studying the sequence determinants of protein folding.

We have developed a phage display system that provides a means to select variants of the IgG binding domain of peptostreptococcal protein L that fold from large combinatorial libraries. The premise underlying the selection scheme is that binding of protein L to IgG requires that the protein be properly folded. Using a combination of molecular biological and biophysical methods, we show that this assumption is valid. First, the phage selection procedure strongly selects against a point mutation in protein L that disrupts folding but is not in the IgG binding interface. Second, variants recovered from a library in which the first third of protein L was randomized are properly folded. The degree of sequence variation in the selected population is striking: the variants have as many as nine substitutions in the 14 residues that were mutagenized. The approach provides a selection for "foldedness" that is potentially applicable to any small binding protein.

The value of the bone scan in idiopathic regional migratory osteoporosis.

Idiopathic regional migratory osteoporosis is a self-limited entity of unknown origin, which has received little attention in the nuclear medicine literature. It is characterized by severe joint pain, typically in a hip, with normal laboratory and normal early radiographic findings. Spontaneous recovery occurs, but recurrence is frequent in another joint, often the opposite hip. Recurrence in the same joint has never been reported. The bone scan is shown to be positive with first symptoms and is important in the diagnosis and management of this entity. Three cases are presented.

Mucous plugging simulating pulmonary embolism in patients with quadriplegia.

Two quadriplegic patients suddenly lost consciousness and were found to have an elevated alveolar-arteriolar oxygen gradient. Their chest x-ray films were normal. Perfusion scintiscans of their lungs showed large areas with markedly reduced or absent perfusion. Ventilation scintiscans demonstrated absent or decreased ventilation to the hypoperfused areas, suggesting mucous plugging. In quadriplegic subjects who have an ineffective cough, acute mucous plugging can produce the sudden onset of hypoxia with essentially normal chest x-ray films, thus mimicking acute pulmonary embolism.

Tumor detection with 67Ga-citrate: a literature survey (1970--1978).

Gallium scan detection of various neoplasms is tabulated by anatomic and histologic categories. The experience with many neoplasms is sufficient to accurately predict the likelihood of detection with gallium. This tabulation helps to point out other areas where the cumulative experience is insufficient to accurately predict sensitivity rates.

Patency evaluation of a LeVeen shunt using 99mTc-sulfur colloid.

The LeVeen shunt has proved valuable in relieving intractable ascites. It is however subject to failure in about 5--8% of cases. To our knowledge there are only three reports in the literature describing the use of nuclides to assess patency; two using 99mTc-sulfur colloid and one using 99mTc-albumin. The purpose of this paper is to add our experience to the data currently published and stress that late liver visualization may occur with an obstructed shunt.

The "mucous plug syndrome". A pulmonary embolism mimic.

Reported are ten instances of major bronchial obstruction by mucous plugs in eight patients during which the clinical features resembled pulmonary embolism. Perfusion lung studies showed significantly diminished perfusion of the involved portions of the lungs. The chest radiographs generally did not, however, reflect the severity of the airway obstruction and in some instances were completely normal. The ventilation studies indicated the extent and severity of the obstruction and matched with the perfusion scans. Pulmonary arteriograms were performed in three patients and gave direct evidence of focally diminished lung perfusion without embolism. The physiologic mechanisms underlying the condition are discussed.

Poorly differentiated lymphocytic lymphoma with ectopic parathormone production: visulization of metastatic calcification by bone scan.

Metastatic soft tissue calcification is known to occur in hypercalcemia and is usually present in the kidneys, stomach and lungs. 1--3 This case presents two unusual features: 1) ectopic parathormone production in association with poorly differentiated lymphocytic lymphoma; and and 2) uptake of 99mTc-pyrophosphate in the liver in the absence of demonstrable abnormality at autopsy. The more usual sites of metastatic calcification also showed uptake of the radionuclide. We will discuss metastatic soft tissue calcification, ectopic parathyroid hormone production, hypercalcemia in malignancy and bone scan agent localization in soft tissues.

Radionuclide brain scan findings in superior sagittal sinus thrombosis.

Superior sagittal sinus thrombosis is a serious condition requiring early diagnosis. This paper presents our experience with two cases and describes the findings. In one case radionuclide brain imaging was the first study performed. In the other, the diagnosis was made at arteriography with scanning used for follow-up.

Bone scanning in detecting soft tissue abnormalities.

With bone scanning, as in other imaging modalities, important clues may be overlooked if attention is too much forcused on the major features displayed. In discussing bone scanning we have avoided the more obvious focal bone abnormalities and addressed our observations to peripheral changes, predominantly of soft tissues.

Crossed fused ectopia with a blind left ureter in a young woman with Turner's syndrome: sonographic and radiological demonstration of a previously undescribed variant.

A previously undocumented variant of crossed fused ectopia in a young woman with Turner's syndrome is reported, with emphasis on sonographic and radiological techniques for diagnosis and subsequent evaluation.

Emission tomography of the kidney.

Single photon emission computerized tomography (SPECT) was done on two patients with suspected renal masses. Nuclear scintigraphy was equivocal on two tumors readily identified by SPECT. Single photon tomography is cost effective and increases the reliability of nuclear scintigraphy.

Radionuclide bone imaging as a means of differentiating loosening and infection in patients with a painful total hip prosthesis.

Twenty patients with 23 painful total hip prostheses were examined by radionuclide imaging (20 cases), arthrography (11 cases), needle aspiration (9 cases), and surgery (19 cases) for the purpose of assessing loosening and/or infection. Bone imaging was most accurate, showing three main distributions of activity: (a) ectopic calcification, (b) focal increased activity at the upper and lower ends of the femoral prosthesis, and (c) diffuse activity. These findings suggest that infection and loosening can be differentiated in many instances. None of the patients with focal activity had infection, compared to 2 of the 3 patients with diffuse uptake.

Ventilation-perfusion imaging and pulmonary angiography: changing pattern of use.

The hospitals and departmental records of the University of Virginia Medical Center from 1976 to 1980 show an increasing frequency of ventilation studies relative to perfusion studies and a decrease in frequency of ventilation-perfusion diagnosis of pulmonary embolus. Pulmonary angiograms have increased from one per 68 nuclear studies to one per 14. A review of 70 patients with correlating angiography or autopsy shows that 89% of nuclear studies were accurate. We have revised our interpretation criteria and indications for pulmonary angiography.